"It is generally assumed that the brain generates behavior through the electrical activity of neurons. Information coding relies on coordinated activity of neuronal assemblies. This cooperative activity of central neurons is embodied in the oscillations and synchronization of neuronal activity among different frequencies bands. The mechanisms allowing the emergence of neuronal oscillations are variable and include fast synaptic transmission and electrical coupling between interneurons or principal cells but their speific role in each frequency domain remains to be elucidated. The implication of inerneuronal gap junctions in hippocampal gamma oscillations has been demonstrated using mice lacking the neuronal connexin gene Cx36. However, the study of the implication of electrical synapses in theta oscillations and ripples (ultrafast oscillations) has led to controversial results, and suggests that other coupled networks expressing other connexins might be involved. This project (outgoing phase) aims at testing the impact of different ellectrically coupled networks (interneurons and pyramidal cells) in hippocampal network activity and hippocampus-dependent learning. For this purpose, hippocampal rhythms will be compared in Cx36 (expressed in interneurons) knocked-out mice, and Cx36 and Cx45 (expressed in pyramidal cells) double KO mice. This will be done using large-scale recordings of unit activity and local-field potential recordings in animals chronically implanted with 16-site silicon probes, during spontaneous episodes of slow-wave and rapid eye movement sleep, wheel running and alternation task. During this post-doctoral training, I will learn large-scale recordings and analysis of neuronal population activity in the hippocampus in behaving animals. The return phase will be dedicated to the application of these techniques in basal ganglia structures, where neuronal oscillations are a crucial pathophysiological issue, notably in Parkinson's disease."